Spectroscopic investigation on interaction of the bioactive component dl-tetrahydropalmatine to bovine serum albumin

The binding of dl-tetrahydropalmatine (dl-THP) with bovine serum albumin (BSA) was investigated by fluorescence spectroscopy, synchronous fluorescence and UV-vis absorption spectroscopy under physiological conditions. The spectroscopic analysis of the emission quenching at different temperatures revealed that the quenching mechanism of bovine serum albumin by dl-THP was dynamic quenching mechanism, and the hydrophobic interaction was the predominant intermolecular force stabilizing the complex. The binding sites number n and apparent binding K were obtained at various temperatures. The thermodynamic parameters were calculated according to the Vant't Hoff equation and the result indicated that Delta H-0 and Delta S-0 are positive value 133.34 kJ mol(-1) and 519.13 J mol(-1)K(-1), respectively. The distance r between dl-THP and the protein was evaluated according to the theory of Forster energy transfer. The results of synchronous fluorescence spectra and UV-vis absorption spectra show that the conformation of BSA has been changed at the presence of dt-THP. (c) 2007 Elsevier B.V. All rights reserved.